The present invention relates to an agricultural mulch. More specifically, the mulch is made from a fibrous web of cellulose fibers having a breaking length from about 1.0 kilometers to about 6.20 kilometers. The web is surface coated with a coating containing a latex at an add on from at least about 30 dry parts coating per 100 parts fiber by weight to form the coated web. The coating at least partially saturates the web to increase both the dry and wet strength of the mulch with the coated web having an average strength of at least about 50 kilograms/square centimeter, a ratio of wet strength to dry strength ranging from at least 0.25 to about 0.7 and a Gurley.RTM.porosity of at least 200 seconds per 100 cubic centimeters of air displacement. Optionally, the fibrous web of cellulose fibers may contain a wet-strength resin to increase the wet strength of the mulch.
In addition to its use as an agricultural mulch, the material of the present invention may be suitable for other applications including bags and outer covers for personal care absorbent products such as diapers, feminine pads, training pants, incontinence products and wound dressings. Other possible applications include surgical drapes and gowns as well as other disposable items.
Biodegradability has become one of the most important, discussed and researched topics as the beginning of a new century approaches. The topic of biodegradability is being researched for a wide variety of products and materials. Plastics, however, are the materials which are getting the most attention when it comes to biodegradability. Plastics are often regarded as not being biodegradable because of the length of time it takes to break these materials down. Examples of such materials include: polyethylene, polypropylene, poly vinyl chloride, and most polyesters. A problem though in discussing the term biodegradability is the term itself. There are an abundance of definitions as to what is biodegradable and what biodegradability means from the standpoint of time and end degradation components.
A factor in determining biodegradability is the amount of oxygen and moisture available for the degradation process. Recent articles such as "Rubbish-" by William L. Rathje, The Atlantic Monthly, Dec. 1989, pg. 99-109, indicate that many landfills have insufficient oxygen and moisture to permit aerobic decomposition. One example given in the above article involved the excavation of a landfill which revealed newspapers from 1959 which were completely legible and in near perfect condition. Thus it can be seen that even materials such as newsprint, which is considered very biodegradable, will not degrade unless given the proper conditions.
One type of disposal which is fairly aerobic is composting. When certain materials are chopped and then mixed in with the top soil, an environment is created which is fairly conducive to degradation. Here again, however, some materials are more predisposed to degrading than others. For example, polyolefin films take lengths of time which are magnitudes greater than paper to break down. Today, many plastics are being mixed and extruded with other constituents, such as starch, to help them break down faster. But even in these cases the time to degrade is much longer than common paper. It is therefore an object of the present invention to provide a material which will degrade significantly when mulched and composted into the soil and yet will have the useful properties of many plastic films.
Thin plastic films are widely used today as replacements for paper. Perhaps one of the most common reasons plastics and especially plastic films are used instead of paper is the strength of plastics in both the wet and dry state. In addition, plastic films have gained their own niche due to the inherent properties of plastic. Examples of the widespread use of plastic include plastic bags, plastic wrap and outer covers for disposable products such as diapers, training pants, incontinence products and sanitary napkins. In all such cases the plastic is usually low cost, lightweight and high in strength in both the wet and dry states. As a result, at least from a convenience standpoint, products including these plastics are readily utilized by the consumer.
The agricultural field is another area where plastics are gaining wider use, particularly with respect to mulches. Plastic mulches are large strips of material which are laid down between and/or around plants to control weeds, soil temperature and erosion. Under such conditions, the plastic has sufficient strength and integrity to withstand the rigors of usage including wind and rain. Despite these advantages, however, disposal becomes a problem. At some point in the agricultural cycle, the mulch must either be removed, burned, tilled or disked into the ground. Removal is very time consuming and disking over time can result in the creation of a top soil layer laden with undecomposed or slowly decomposing plastic.
It is therefore an object of the present invention to provide a cellulose-based material which will have sufficient strength and barrier properties to act as a replacement for the above products while also having a sufficient degree of biodegradability. It is also an object to make this material as low cost as possible.
These and other objects of the present invention will become more apparent upon a further review of the following specification and claims.